This application is a 371 of PCT GB96/03218 Dec. 23, 1996.
This invention relates to new 1-hydroxy pregnacalciferol derivatives, more especially to 1-hydroxy pregnacalciferol derivatives having anti-progesterone activity.
Vitamin D3 has long been known to play a key role in the metabolism of calcium. The discovery that the D vitamins undergo hydroxylation in vivo led to the synthesis of many analogues of vitamin D whose evaluation indicated that hydroxyl groups at the 1xcex1-position and at either the 24R- or 25-position were essential for the compound or metabolite thereof to exhibit a substantial effect on calcium metabolism.
Subsequent work indicated that the natural metabolite 1xcex1,25-dihydroxy vitamin D3 exhibited cell modulating activity, including stimulation of cell maturation and differentiation, as well as immunosuppressive effects, and also exhibited an immunopotentiating effect, stimulating the production of bactericidal oxygen metabolites and the chemotactic response of leukocytes.
The therapeutic potential of 1xcex1,25-hydroxy vitamin D3 in these areas is, however, severely limited by its potent effect on calcium metabolism. Thus dosages at a level sufficient to elicit a desired cell modulating, immunosuppressive or immunopotentiating effect tend to lead to unacceptable hypercalcaemia. Considerable interest has therefore been shown in the synthesis of analogues having reduced effects on calcium metabolism but still exhibiting desired effects on cellular metabolism, e.g. as summarised in WO 95/16672.
DeLuca and coworkers (Tetrahedron Letters 35(15) (1994), pp. 2295-2298 and Program Abstracts, 77th Annual Meeting of the Endocrine Society (1995), Abstract No. P2-662, p.456) have reported that in their investigations of such vitamin D analogues they have tested various 20-oxopregnacalciferols and found them to be inactive as regards effect on calcium metabolism. Noting that these compounds shared some structural features with progesterone and aware of the development of compounds such as RU 486, a 19-nor steroid having the formula 
and exhibiting strong anti-progesterone and anti-glucocorticosteroid activities, they also tested these compounds for ability to bind to the progesterone receptor. 20-Oxopregnacalciferols, and to a lesser extent the 22-aldehyde and 22-hydroxy calciferols, were found to bind the progesterone receptor. Of xe2x80x9cmany otherxe2x80x9d vitamin D analogues tested no other showed significant binding activity. 1xcex1-Hydroxy-20-oxopregna-calciferol and its corresponding 19-nor analogues are specifically stated not to have such binding effect.
In contrast to RU 486, 20-oxopregnacalciferol is said not to bind to the glutocorticoid receptor but has been found (Program Abstracts, 76th Annual Meeting of the Endocrine Society (1994), Abstract No. 1744, p. 636) to suppress in vitro growth of human breast cancer cells (T47D).
The present invention is based on the surprising finding that a number of 1-hydroxy pregnacalciferols, in complete contradiction to the findings of DeLuca et al., do in fact act as potent antagonists of progesterone activity, for example as evidenced by antifertility (e.g. contraceptive) activity, anti-progesterone assay and inhibition of growth of mammary cancer T47D and MCF-7 cell lines. Even more surprisingly, we have found that the anti-progesterone effects in respect of these 1-hydroxy compounds may exceed those of the corresponding 1-desoxy compounds.
Apart from the compound 1xcex1-hydroxy-20-oxopregnacalciferol, insofar as it may have been disclosed by DeLuca et al., these 1-hydroxy pregnacalciferols and their O-protected derivatives are novel and constitute a feature of the invention.
Thus according to one aspect of the invention there are provided compounds of general formula (I): 
(wherein R1 denotes an optionally protected hydroxyl group or a lower alkoxy group and R2 denotes a lower alkynyl group optionally substituted by a hydroxyl, protected hydroxyl or lower alkoxy group; or R1 denotes a group xe2x80x94C(RA)(RB)CH3 wherein RA is a lower alkynyl group optionally substituted by a hydroxyl, protected hydroxyl or lower alkoxy group and RB is an optionally protected hydroxyl group or a lower alkoxy group, or RA and RB together represent an oxo group, and R2 denotes a hydrogen atom, an optionally protected hydroxyl group or a lower alkoxy group; and R3 and R4, which may be the same or different, each denote a hydrogen atom or an O-protecting group) and the corresponding 5,6-trans (i.e. 5E-isomers) thereof, with the proviso that when R1 denotes a group xe2x80x94C(RA)(RB)CH3 wherein RA and RB together denote an oxo group and the group xe2x80x94OR4 is in the xcex1-configuration then R2 is other than hydrogen.
Where any of R1, R2 and RB denote or contain lower alkoxy groups these may, for example, be C1-6 alkoxy groups such as methoxy, ethoxy, propoxy and butoxy groups which, where appropriate, may be straight chain or branched.
Where R2 or RA denotes a lower alkynyl group this may, for example, contain up to 6 carbon atoms, and may for example be an alk-l-yn-1-yl group such as ethynyl, 1-propynyl, 1-butynyl, 1-pentynyl or 1-hexynyl, or an xcfx89-alkynyl group such as propargyl. Hydroxyl or lower alkoxy substituents may be present as in, for example, 3-hydroxypropynyl and 3-methoxypropynyl groups.
Where R3 and R4 represent O-protecting groups these may, for example, be cleavable O-protecting groups such as are commonly known in the art. Suitable groups include etherifying groups such as silyl groups (e.g. tri(lower alkyl)silyl groups such as trimethylsilyl, triethylsilyl, triisopropylsilyl or t-butyldimethylsilyl; tri(aryl)silyl groups such as triphenylsilyl; and mixed alkyl-arylsilyl groups); lower (e.g. C1-6) alkyl groups optionally interrupted by an oxygen atom, such as methyl, methoxymethyl or methoxyethoxymethyl; and cyclic groups such as tetrahydropyranyl. Esterifying O-protecting groups include lower (e.g. C1-6) alkanoyl such as acetyl, propionyl, isobutyryl or pivaloyl; aroyl (e.g. containing 7-15 carbon atoms) such as benzoyl or 4-phenylazobenzoyl; lower alkane sulphonyl such as (optionally halogenated) methane sulphonyl; and arene sulphonyl such as p-toluene sulphonyl.
O-protected derivatives are useful as intermediates in the preparation of active 1,3xcex2-diols of formula (I). Additionally, where the O-protecting groups are metabolically labile in vivo, such ethers and esters of formula (I) may be useful directly in therapy.
5,6-Trans isomers of compounds of general formula (I) are useful as intermediates in the preparation of the corresponding 5,6-cis isomers, e.g. as described in greater detail hereinafter. Where R3 and R4 denote hydrogen atoms or metabolically labile groups such 5,6-trans isomers may, however, exhibit biological activity, although typically at a lower order of magnitude than corresponding 5,6-cis isomers, and thus may be useful in therapy.
The anti-progestational activity of both 1xcex1-hydroxy-20-oxopregnacalciferol and active compounds of general formula (I) as defined above suggests their use as, for example, antiproliferative agents in, for example, the treatment and/or prevention of hormone responsive tumours or hyperplasias (such as breast, prostate or ovarian cancers, fibroids or endometriosis) or as suppressants of progesterone activity, for instance in oedema, acne, melasma or in fertility control (such as, for example, in inducing abortion or in contraception) in human or animal subjects. The invention accordingly embraces the use of these compounds both in treatment or prophylaxis of the above-mentioned conditions and in the manufacture of medicaments for such treatment or prophylaxis.
Whilst the antiproliferative effect of compounds according to the present invention is somewhat lower than that of 1xcex1-hydroxy vitamin D analogues having cell modulating activity, for example as described in our International Patent Applications Nos. WO-A-9309093, WO-A-9426707, WO-A-9503273, WO-A-9516672 and WO-A-9525718, it is nonetheless significant and may be therapeutically useful since the compounds have an extremely low effect on calcium metabolisum and thus exhibit an advantageous therapeutic ratio. They may therefore find use in any of the applications described in the aforementioned WO-A-9309093, WO-A-9426707, WO-A-9503273, WO-A-9516672 and WO-A-9525718, the contents of which are incorporated herein by reference, for example as immunosuppressive and/or antiinflammatory agents.
It will be appreciated that compounds according to the invention may exhibit different activity profiles as regards their antineoplastic, antifertility, antiproliferative, immunosuppressive and/or antiinflammatory activity etc. Routine bioassay procedures may be used in known manner to select particular compounds most suited to particular therapeutic applications.
Active compounds according to the invention may be formulated for administration by any convenient route, e.g. orally (including sublingually), parenterally, rectally or by inhalation; pharmaceutical compositions so formulated comprise a feature of the invention.
Orally administrable compositions may, if desired, contain one or more physiologically compatible carriers and/or excipients and may be solid or liquid. The compositions may take any convenient form including, for example, tablets, coated tablets, capsules, lozenges, aqueous or oily suspensions, solutions, emulsions, syrups, elixirs and dry products suitable for reconstitution with water or another suitable liquid vehicle before use. The compositions may advantageously be prepared in dosage unit form. Tablets and capsules according to the invention may, if desired, contain conventional ingredients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth or polyvinyl-pyrollidone; fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; lubricants, for example magnesium stearate, talc, polyethylene glycol or silica; disintegrants, for example potato starch; or acceptable wetting agents such as sodium lauryl sulphate. Tablets may be coated according to methods well known in the art.
Liquid compositions may contain conventional additives such as suspending agents, for example sorbitol syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxymethylcellulose, carboxymethylcellulose, aluminium stearate gel or hydrogenated edible fats; emulsifying agents, for example lecithin, sorbitan monooleate or acacia; non-aqueous vehicles, which may include edible oils, for example vegetable oils such as arachis oil, almond oil, fractionated coconut oil, fish-liver oils, oily esters such as polysorbate 80, propylene glycol, or ethyl alcohol; and preservatives, for example methyl or propyl p-hydroxybenzoates or sorbic acid. Liquid compositions may conveniently be encapsulated in, for example, gelatin to give a product in dosage unit form.
Compositions for parenteral administration may be formulated using an injectable liquid carrier such as sterile pyrogen-free water, sterile peroxide-free ethyl oleate, dehydrated alcohol or propylene glycol or a dehydrated alcohol/propylene glycol mixture, and may be injected intravenously, intraperitoneally or intramuscularly.
Compositions for rectal administration may be formulated using a conventional suppository base such as cocoa butter or another glyceride.
Compositions for administration by inhalation are conveniently formulated for self-propelled delivery, e.g. in metered dose form, for example as a suspension in a propellant such as a halogenated hydrocarbon filled into an aerosol container provided with a metering dispense valve.
It may be advantageous to incorporate an antioxidant, for example ascorbic acid, butylated hydroxyanisole or hydroquinone in the compositions of the invention to enhance their storage life.
Where any of the above compositions are prepared in dosage unit form these may for example contain 0.5-2500 xcexcg, e.g. 1-500 xcexcg, of active compound according to the invention per unit dosage form. The compositions may if desired incorporate one or more further active ingredients, for example antiprogresterones such as RU 486, oestrogens or oestrogen antagonists.
A suitable daily dose of an active compound according to the invention may for example be in the range 1-5000 xcexcg, e.g. 2-1000 xcexcg, per day, depending on factors such as the severity of the condition being treated and the age, weight and condition of the subject.
Compounds according to the invention may be prepared by any convenient method, for example involving one or more of the following:
A) By isomerisation of a corresponding 5,6-trans compound, preferably in 1,3-di(O-protected) form. Isomerisation may be effected by, for example, treatment with iodine, with a disulphide or diselenide, or by irradiation with ultraviolet light, preferably in the presence of a triplet sensitiser. Such 5,6-trans compounds may themselves be prepared by oxidising a corresponding 1-desoxy-5,6-trans compound using a selenite ester or selenium dioxide or selenous acid in the presence of an alcohol, e.g. as described in GB-A-2038834, the contents of which are incorporated herein by reference. This process will generate the corresponding 1xcex1- and 1xcex2-hydroxy compounds as major and minor products respectively; these may readily be separated, e.g. by chromatography. The 1-desoxy-5,6-trans starting material may, if desired, be prepared in situ by isomerisation of the corresponding 1-desoxy-5,6-cis compound under the conditions of the oxidation.
B) By oxidising a compound (I) or corresponding 5,6-trans isomer in which RA and RB together denote an oxo group and R2 denotes a hydrogen atom, preferably in 1,3-di(O-protected) form, or a corresponding 1-desoxy compound, to yield a compound in which R2 denotes a hydroxyl group. Such oxidation may, for example, be effected using Barton/Gardner hydroxylation conditions, e.g. by passing air through a solution of the compound in one or more polar organic solvents, for example selected from cyclic ethers such as tetrahydrofuran and tertiary amides such as N,N-dimethylformamide, in the presence of a strong base, e.g. an alkali metal lower alkoxide such as potassium t-butoxide, preferably in the presence of the corresponding lower alkanol, e.g. t-butanol. The reaction is preferably carried out in the presence of a low valence phosphorus compound capable of reducing a hydroperoxide group to a hydroxyl group, for example a phosphine or phosphite, e.g. a tri(lower alkyl)phosphite such as triethylphosphite. Surprisingly it has been found that neither these severe oxidative conditions nor the reactive 17-hydroperoxide intermediate which is transiently formed react with or degrade the sensitive triene system present in the molecule. This unexpectedly effective and useful hydroxylation procedure accordingly constitutes a feature of the present invention. Where a 1-desoxy compound is prepared using this process it may subsequently be 1-hydroxylated, for example by oxidation using an appropriate selenium compound as described in (A) above to introduce a 1xcex1-hydroxyl group.
C) By reaction of a preferably 1,3-di(O-protected) compound of formula (I) or corresponding 5,6-trans isomer in which R1 and R2 together or RA and RB together denote an oxo group with a lower alkynyl anion to yield a compound of formula (I) in which R1 or RA is lower alkynyl and R2 or RB is hydroxy. The lower alkynyl anion may be added in the form of a salt (e.g. an alkali metal salt such as a lithium salt) of the appropriate lower alkyne, if desired in the form of a complex with an appropriate material, for example a diamine, e.g. a lower alkylenediamine such as ethylenediamine, 1,2-diaminopropane or 1,3-diaminopropane, or it may be generated, if desired in situ, by treatment of the corresponding lower alkyne with a strong base such as sodium amide, lithium diisopropylamide or n-butyllithium. Alternatively the anion may be generated in situ from a corresponding silylated lower alkyne by reaction with a source of fluoride ion, for example anhydrous quaternary ammonium fluoride such as tetrabutylammonium fluoride. If this reaction is performed on a compound (I) in which RA and RB together denote an oxo group and R2 denotes a hydroxyl group (e.g. prepared as in (B) above), this hydroxyl group will be correspondingly silylated during the course of the reaction. If the protecting groups are appropriately selected, e.g. if the 1- and 3-positions are protected as triisopropylsilyloxy groups and the R2 hydroxy group as trimethylsilyloxy, this latter group may be selective cleaved, for example by mild acid hydrolysis, e.g. using acetic acid or dilute hydrochloric acid.
D) By alkylating a preferably 1,3-di(O-protected) compound (I) or corresponding 5,6-trans isomer in which R1, R2 or RB denotes a hydroxyl group to generate a corresponding compound in which R1, R2 or RB denotes a lower alkoxy group. Such alkylation may conveniently be effected by reaction with an alkylating agent such as a lower alkyl sulphonate or halide (e.g. chloride, bromide or, more preferably, iodide) in the presence of a base such as a metal hydride, e.g. an alkali metal hydride such as sodium or potassium hydride.
It will be appreciated that any of the above steps may be followed by removal of any O-protecting groups as necessary and/or desired, and that where more than one of the above steps is employed they may be used in any appropriate order.
In general, O-protecting groups present at the 1- and/or 3xcex2-positions may be removed by, for example, conventional methods such as are well documented in the literature. Thus esterifying acyl groups may be removed by basic hydrolysis, e.g. using an alkali metal alkoxide in an alkanol. Etherifying groups such as silyl groups may be removed by acid hydrolysis or treatment with a fluoride salt, e.g. a tetraalkylammonium fluoride. The use of such acid-labile but base-stable protecting groups may be of advantage when reactions involving strongly basic conditions are employed, e.g. in steps (C) and (D) above. Removal of such protecting groups will typically be performed as a final stage of a preparative sequence.
It will be appreciated that starting materials for step (B) above include 1xcex1-hydroxy-20-oxo-cholecalciferol and its O-protected derivatives, which are known compounds. Such compounds may be converted to corresponding compounds (I) in which R1 and R2 together denote an oxo group, i.e. useful starting materials for step (C) above, e.g. by oxidation using techniques analogous to those for Barton/Gardner hydroxylation, the normally air-sensitive triene system of the compounds proving surprisingly stable under such oxidative conditions. Such 17-ones of formula (I) where R1 and R2 together denote an oxo group are themselves novel and, together with the above-described method for their preparation, represent further features of the invention. 1-Desoxy analogues of such 17-ones may similarly be prepared and subsequently 1-hydroxylated, e.g. by oxidation using an appropriate selenium compound as described in (A) above to effect 1-hydroxylation.
The following non-limitative Examples serve to illustrate the invention. All temperatures are in xc2x0 C.
Air was passed through a solution of 1xcex1,3xcex2-bis-triisopropylsilyloxy-20-oxo-5,6-transpregnacalciferol [5,6-trans analogue of compound (I) where R1=CH3CO, R2=H, R3=R4=(i-Pr)3Si] (620 mg) in t-butanol (10 ml) containing potassium t-butoxide (6 ml of a 1M solution in tetrahydrofuran) maintained at 0xc2x0. After 3 hours the flow of air was stopped, the reaction mixture was purged with argon for 20 minutes, heated under reflux for 20 minutes, diluted with ether and worked up to give the title compound (250 mg isolated by chromatography): UV (Et2O) xcexmax 268, xcexmin 228 nm; IR (CDCl3) 1630, 1730 cmxe2x88x923; NMR (CDCl3) xcex4 0.7 (s, 18-H""s), 3.9-4.6 (m, 1,3-H""s), 4.6-5.0 (bs, 19-H""s), 5.3-6.3 (ABq, 6,7-H""s).
Air was passed through a solution of 3xcex2-triisopropylsilyloxy-20-oxo-5,6-transpregnacalciferol [1-desoxy-5,6-trans analogue of compound (I) where R1=CH3CO, R2=H, R3=(i-Pr)3Si] (460 mg) in t-butanol (10 ml) containing potassium t-butoxide (2.5 ml of a 1M solution in tetrahydrofuran) maintained at 0xc2x0. Further portions of potassium butoxide (3xc3x972.5 ml of a 1M solution in tetrahydrofuran) were added at half hour intervals, whereafter the flow of air was stopped, the reaction mixture was purged with argon for 30 minutes, diluted with ether and worked up to give the title compound (190 mg isolated by chromatography): IR (CDCl3) 1610, 1720 cmxe2x88x921.
This compound can be converted to the product of Preparation 1 by oxidation as described in GB-A-2038834 and appropriate silylation of the 1xcex1-hydroxy compound so obtained.
Air was passed through a solution of 1xcex1,3xcex2-bis-triisopropylsilyloxy-20-oxo-5,6-transpregnacalciferol [5,6-trans analogue of compound (I) where R1=CH3CO, R2=H, R3=R4=(i-Pr)3Si] (490 mg) in t-butanol (7.5 ml) containing potassium t-butoxide (4 ml of a 1M solution in tetrahydrofuran) maintained at 0xc2x0. After 2.5 hours the flow of air was stopped, the reaction mixture was purged with argon for 20 minutes, diluted with ether and worked up to give the title compound (250 mg isolated by chromatography): IR (CDCl3) 3600-3100, 1620 cmxe2x88x921.
This compound can be converted to the product of Preparation 1 by heating in the presence of base, e.g. an alkali metal alkoxide such as potassium t-butoxide.